The study examined 50 houses around Raleigh in North Carolina and found that while the age of the house did not affect the number of bugs found, the average local income did.
Photograph: Rosa Betancourt/Alamy Stock Photo

Homes in wealthier areas harbour more bugs, containing up to 200 different species of flies, spiders, beetles and ants, according to new research. The vast majority are not pests although dust mites and book lice were also common.

The finding is the latest demonstration of the “luxury effect” which has shown that richer neighbourhoods are more biologically diverse in plants, birds, bats and lizards, largely thanks to the greater number and variety of plants in gardens and parks. But it is the first time the effect has been shown for arthropods, either inside or outside homes.

The researchers said the work overturns the “general perception” that homes in poorer neighbourhoods host more indoor arthropods. “Our unexpected, and perhaps counterintuitive finding highlights how much we have yet to learn about indoor ecology,” said the scientists led by Misha Leong at the California Academy of Sciences.

The study, published in Biology Letters, examined 50 houses around Raleigh in North Carolina and found that while the age of the house did not affect the number of bugs found, the average local income did, along with the size of the house and the density and variety of plants in the local area.

The effect of income was particularly important, with homes in richer areas with relatively bare gardens still containing plenty of bugs, thanks to the more verdant neighbourhood. “It matters, in short, not only how much vegetation you have in your yard, but how much is present in the yards and other habitats nearby,” the researchers said.

“As more of the planet becomes urbanised, the proportion of the ecological world potentially influenced by human socioeconomics will increase,” said the scientists. “Our work suggests that the management of neighbourhoods and cities can have effects on biodiversity that can extend from trees and birds all the way to the arthropod life in bedrooms and basements.”

The main cause of the luxury effect is the greater numbers of plants and this is linked to the average wealth of a neighbourhood because richer people have more money to spend on gardening. More plants mean more habitat and food for animals and bugs, some of which find their way into homes. “Indoor arthropod diversity is, in part, a reflection of the world outdoors,” the researchers said.

Paul Hetherington, at UK conservation charity Buglife, said: “These findings highlight the need for urban planners and housing developers to factor in to all areas, especially dense housing, the provision of adequate wild space for nature, creating stepping stones across the urban landscape and helping to connect everyone to nature.”

Leong’s team said houses were very attractive traps for insects: “In respect to arthropods, houses act as exceptional traps; passively collecting like Malaise traps, but also acting as light and bait traps.”

The research analysed standalone houses in areas with average incomes no lower than $33,000 a year and said more research was needed to investigate the prevalence of bugs in other types of housing and in very poor areas.